JEE Questions for Physics Electrostatics I Quiz 5 - MCQExams.com

Two identical charged spheres suspended from a common point by two massless strings of length l are initially a distance d(d < < l) apart because of their mutual repulsion. The charge begins to leak from both the spheres at a constant rate. As a result charges approach each other with a velocity v. Then, as a function of distance x between them
  • v ∝ x -1
  • v ∝ x 1/2
  • v ∝ x
  • v ∝ x -1/2
Two positive charges of magnitude q are placed at the ends of a side 1 of a square of side 2a. Two negative charges of the same magnitude are kept at the other corners. Starting from rest, if a charge Q moves from the middle of side 1 to the centre of square, its kinetic energy at the centre of square is

  • Physics-Electrostatics I-70483.png
  • zero

  • Physics-Electrostatics I-70484.png

  • Physics-Electrostatics I-70485.png
Charge q2 of mass m revolves around a stationary charge q1 in a circular orbit of radius r. The orbital periodic time of q2 would be

  • Physics-Electrostatics I-70487.png
  • 2)
    Physics-Electrostatics I-70488.png

  • Physics-Electrostatics I-70489.png

  • Physics-Electrostatics I-70490.png
Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle of 30° with each other. When suspended in a liquid of density 0.8 gcm-3, the angle remains the same. If density of the material of the sphere is 1.6 gcm-3, the dielectric constant of the liquid is
  • 4
  • 3
  • 2
  • 1

Physics-Electrostatics I-70493.png

  • Physics-Electrostatics I-70494.png
  • 2)
    Physics-Electrostatics I-70495.png

  • Physics-Electrostatics I-70496.png

  • Physics-Electrostatics I-70497.png
A and B are two identical spherical charged bodies, which repel each other with force F, kept at a finite distance. A third uncharged sphere of the same size is brought in contact with sphere B and removed. It is then kept at mid-point of A and B. Find the magnitude of force on C.
  • F / 2
  • F / 8
  • F
  • Zero
Two identical conducting spheres carrying different charges attract each other with a force F, when placed in air medium at a distance d apart. The spheres are brought into contact and then taken to their original positions. Now the two spheres repel each other with a force, whose magnitude is equal to that of the initial attractive force. The ratio between initial charges on the spheres is

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  • 2)
    Physics-Electrostatics I-70501.png

  • Physics-Electrostatics I-70502.png

  • Physics-Electrostatics I-70503.png

  • Physics-Electrostatics I-70504.png
Two spherical conductors B and C having equal radii and carrying equal charges in them repel each other with a force F, when kept apart at some distance. A third spherical conductor having same radius as that of B, but uncharged is brought in contact with B. then brought in contact with. C and finally removed away from both. The new force of repulsion between B and C is

  • Physics-Electrostatics I-70506.png
  • 2)
    Physics-Electrostatics I-70507.png

  • Physics-Electrostatics I-70508.png

  • Physics-Electrostatics I-70509.png
The bob of simple pendulum is hanging vertically down from a fixed identical bob by means of a string of length l. If both bobs are charged with a charge q each, time period of the pendulum is (ignore the radii of the bobs)

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  • 2)
    Physics-Electrostatics I-70512.png

  • Physics-Electrostatics I-70513.png

  • Physics-Electrostatics I-70514.png
A thin glass rod is bent into a semi-circle of radius R. A charge + Q is uniformly distributed along the upper half and a charge – Q is uniformaly distributed along the lower half. The magnitude of the electric filled at the centre of the semi-circle is

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  • 2)
    Physics-Electrostatics I-70516.png

  • Physics-Electrostatics I-70517.png

  • Physics-Electrostatics I-70518.png
Figure shows the portions of two infinite parallel non-conducting sheets having the magnitude of the surface charge densities σ(+) = 6.8 μ C/m2 and σ(-) = 4.3 μC/m2 for the positively and negatively charged sheets, respectively. Find the electric field E between the sheets.
Physics-Electrostatics I-70520.png
  • 6.3 × 105 N/ C towards right
  • 6.3 × 105 N/ C towards left
  • 1.14 × 105 N/ C towards right
  • 1.41 × 105 N/C towards left
Consider a thin spherical shell of radius R with its centre at the origin, carrying uniform positive surface charge density. The variation of the magnitude of the electric field |E(r) | and the electric potential V(r) with the distance r from the centre, is best represented by which graph?

  • Physics-Electrostatics I-70522.png
  • 2)
    Physics-Electrostatics I-70523.png

  • Physics-Electrostatics I-70524.png

  • Physics-Electrostatics I-70525.png

Physics-Electrostatics I-70527.png
  • The electric field at O is 6k along OD
  • The potential at O is one
  • The potential at all points on the line PR is not same
  • The potential at all points on the line ST is same

Physics-Electrostatics I-70529.png

  • Physics-Electrostatics I-70530.png
  • 2)
    Physics-Electrostatics I-70531.png

  • Physics-Electrostatics I-70532.png

  • Physics-Electrostatics I-70533.png
The figure shows electric field E at a distance r in any direction from the origin O. The electric field E is due to
Physics-Electrostatics I-70535.png
  • a charged hollow metallic sphere of radius OP with centre at O
  • a charged solid metallic sphere of radius OP with centre at O
  • a uniformly charged non-conducting sphere of radius OP with centre at O
  • a uniformly charged non-conducting hollow-sphere of radius OP with centre at O

Physics-Electrostatics I-70537.png
  • zero
  • 2)
    Physics-Electrostatics I-70538.png

  • Physics-Electrostatics I-70539.png

  • Physics-Electrostatics I-70540.png
The potential at a point x (measured in μm) due to some charges situated on the x-axis is given by
V(x) = 20/(x2 – 4)volt
The electric field E at x = 4 μm is given by,

  • Physics-Electrostatics I-70542.png
  • 2)
    Physics-Electrostatics I-70543.png

  • Physics-Electrostatics I-70544.png

  • Physics-Electrostatics I-70545.png
Charges + 2q, + q and +q are placed at the corners A ,B and C of an equilateral triangle ABC. If E is the electric field at the circumcentre O of the triangle, due to the charge +q, then the magnitude and direction of the resultant electric field at O is
  • E along AO
  • 2E along AO
  • E along BO
  • E along CO
  • zero
Consider a neutral conducting sphere. A positive point charge is placed outside the sphere. The net charge on the sphere is then
  • Negative and distributed uniformly over the surface of the sphere
  • Negative and appears only at the point on the sphere closest to the point charge
  • Negative and distributed non-uniformly over the entire surface of the sphere
  • Zero
A solid metallic sphere has a charge + 3Q. Concentric with this sphere is a conducting spherical shell having charge –Q. The radius of the sphere is a and that of the spherical shell is b (b > a). What is the electric field at a distance R (a < R < b) from the centre?

  • Physics-Electrostatics I-70548.png
  • 2)
    Physics-Electrostatics I-70549.png

  • Physics-Electrostatics I-70550.png

  • Physics-Electrostatics I-70551.png
Which of the following plots represents the variation of the electric field with distance from the centre of a uniformly charged non-conducting sphere of radius R?

  • Physics-Electrostatics I-70553.png
  • 2)
    Physics-Electrostatics I-70554.png

  • Physics-Electrostatics I-70555.png

  • Physics-Electrostatics I-70556.png
Three infinitely long charge sheets are placed as shown in figure. The electric field at point P is
Physics-Electrostatics I-70558.png

  • Physics-Electrostatics I-70559.png
  • 2)
    Physics-Electrostatics I-70560.png

  • Physics-Electrostatics I-70561.png

  • Physics-Electrostatics I-70562.png
A charged ball B hangs from a silk thread S, which makes an angle θ with a large charged conducting sheet P, as shown in the figure. The surface charge density σ of the sheet is proportional to
Physics-Electrostatics I-70564.png

  • Physics-Electrostatics I-70565.png
  • 2)
    Physics-Electrostatics I-70566.png

  • Physics-Electrostatics I-70567.png

  • Physics-Electrostatics I-70568.png
Three concentric metallic spherical shells of radii R, 2R ,3R are given charges Q1 , Q2 , Q3 respectively. It is found that the surface charge densities on the outer surfaces of the shells are equal. Then, the ratio of the charges given to the shells, Q1 : Q2 : Q3 is
  • 1 : 2 : 3
  • 1 : 3 : 5
  • 1 : 4 : 9
  • 1 : 8 : 18
A sample of HCl gas is placed in an electric field of 3 × 104 NC -1. The dipole moment of each HCl molecule is 6 x 10-30 Cm. The maximum torque, that can act on a molecule is
  • 2 × 10-34 C2mN-1
  • 2 × 10-34 Nm
  • 18 × 10-26 Nm
  • 0.5 × 1034 C-2mN-1
Which of the following statement(s) is/are correct?
  • If the electric field due to a point charge varies as r-2.5 instead of r-2 , then the Gauss' law will still be valid
  • The Gauss' law can be used to calculate the field distribution around an electric dipole
  • If the electric field between two point charges is zero somewhere, then the sign of the two charges is the same
  • The work not done by the external force in moving a unit positive charge from point A at potential VA to point B at potential VB is (VB - VA)
A long, hollow conducting cylinder is kept coaxially inside another long, hollow conducting cylinder of larger radius. Both the cylinders are initially electrically neutral.
  • A potential difference appears between the two cylinders when a charge density is given to the inner cylinder
  • A potential difference appears between the two cylinders when a charge density is given to the outer cylinder
  • No potential difference appears between the two cylinders when a uniform line charge is kept along the axis of the cylinders
  • No potential difference appears between the two cylinders when same charge density is given to both the cylinders
A hollow cylinder has a charge q coulomb within it. If ϕ is the electric flux in unit of voltmeter associated with the curved surface B, the flux linked with the plane surface A in unit of voltmeter will be
Physics-Electrostatics I-70572.png

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  • 2)
    Physics-Electrostatics I-70574.png

  • Physics-Electrostatics I-70575.png

  • Physics-Electrostatics I-70576.png
The electric flux for Gaussian surface A that enclose the charged particles in free space is (given, q1 = –14 nC, q2 = 78.85 nC, q3 = – 56 nC)
Physics-Electrostatics I-70578.png
  • 103 Nm2 C-1
  • 103 CN-1 m -2
  • 6.32 × 103 Nm2 C -1
  • 6.32 × 103 CN-1m-1
A charge Q is uniformly distributed over a long rod AB of length L as shown in the figure. The electric potential at the point 0 lying at distance L from the end A is
Physics-Electrostatics I-70580.png

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  • 2)
    Physics-Electrostatics I-70582.png

  • Physics-Electrostatics I-70583.png

  • Physics-Electrostatics I-70584.png
A point charge + q moves from points P to O along the path PQRO in a uniform electric field E. Find the work done by the field
Physics-Electrostatics I-70586.png
  • -2qEa
  • 2aEa
  • 8qEa
  • -4qEa
This question has statement 1 and statement 2. Of the four choices given after the statements, choose the one that best describes the two statements.
An insulating solid sphere of radius R has a uniform positive charge density ρ. As a result of this uniform charge distribution, there is a finite value of electric potential at the centre of the sphere, at the surface of the sphere and also at a point outside the sphere. The electric potential at infinite is zero.
Physics-Electrostatics I-70588.png
  • Statement 1 is false, Statement .2 is true
  • Statement 1 is true, Statement 2 is false
  • Statement 1 is true, Statement 2 is true, Statement 2 is the correct explanation for Statement 1
  • Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation for Statement 1
A charge +q is placed at the origin O of X–Y axis as shown in the figure. The work done in taking a charge Q from A to B along the straight line AB is
Physics-Electrostatics I-70590.png

  • Physics-Electrostatics I-70591.png
  • 2)
    Physics-Electrostatics I-70592.png

  • Physics-Electrostatics I-70593.png

  • Physics-Electrostatics I-70594.png
Consider three concentric shells of metal A, B and C are having radii a, b and c respectively as shown in the figure (a < b < c). Their surface charge densities are σ, – σ and σ respectively. Calculate the electric potential on the surface of shell A
Physics-Electrostatics I-70597.png

  • Physics-Electrostatics I-70598.png
  • 2)
    Physics-Electrostatics I-70599.png

  • Physics-Electrostatics I-70600.png

  • Physics-Electrostatics I-70601.png
A small conducting sphere of radius r is lying concentrically inside a bigger hollow conducting sphere of radius R. The bigger and smaller spheres are charged with Q and q (Q > q) and are insulated from each other. The potential difference between the spheres will be

  • Physics-Electrostatics I-70603.png
  • 2)
    Physics-Electrostatics I-70604.png

  • Physics-Electrostatics I-70605.png

  • Physics-Electrostatics I-70606.png
Figure shows three points A ,B and C in a region of uniform electric field E. The line AB is perpendicular and BC is parallel to the field lines. Then, which of the following holds good?
where, VA ,VB and VC represent the electric potential at the points A ,B and C respectively.
Physics-Electrostatics I-70608.png
  • VA =VB =VC
  • VA =VB > VC
  • VA =VB < VC
  • VA > VB =VC
Two thin wire rings each having a radius R are placed at a distance d apart with their axes coinciding. The charges on the two rings are + q and –q. The potential difference between the centres of the two rings is

  • Physics-Electrostatics I-70609.png
  • 2)
    Physics-Electrostatics I-70610.png
  • zero

  • Physics-Electrostatics I-70611.png
Two point charges +4µC and + 2µC repel each other with a force of 8 N. If a charge of –4µC is added to each of these charges, the force would be
  • Zero
  • 8N
  • 4N
  • 12N
A charge Q is placed at the centre of the line joining two point charges + q and + q, (Fig). What is the ratio Q/q for the system to be in equilibrium?
Physics-Electrostatics I-70613.png
  • 4
  • 1/4
  • –4
  • – 1/4
A charge q1 exerts some force on a second charge q2. If third charge q3 is brought near, the force of q1 exerted on q2
  • decreases
  • increases
  • remains unchanged
  • increases if q3 is of same sign as q1 and decreases if q3 is of opposite sign
Two charges q1 and q2 are distance a apart. If dielectric of thickness b and dielectric constant K is inserted in between the two charges, the force experienced would be

  • Physics-Electrostatics I-70616.png
  • 2)
    Physics-Electrostatics I-70617.png

  • Physics-Electrostatics I-70618.png
  • None of these
The surface density on the copper sphere is σ. The electric field strength on the surface of the sphere is
  • σ
  • σ/2
  • σ/2 ∈0
  • σ/∈0
An electric field exists in the space around a point charge +Q. A positive charge +q is carried from A to B and A to C, where B and C lie on a circle with +Q at the centre (Fig.). Work done is
Physics-Electrostatics I-70619.png
  • greater along the path AC than along AB
  • greater along the path AB than along AC
  • same in both the cases
  • zero in both the cases
A uniform electric field having a magnitude E 0 and direction along the positive X -axis exists. If the potential V is zero at x = 0, then its value at x = + x will be
  • V(x) = +x E0
  • V(x) = – x E0
  • V(x) = +x2 E0
  • V x = – x2 E0
An electron of mass m and charge e is accelerated from rest through a potential difference V in vacuum. Its final speed will be

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  • 2)
    Physics-Electrostatics I-70623.png

  • Physics-Electrostatics I-70624.png

  • Physics-Electrostatics I-70625.png
A spherical charged conductor has surface density of charge = σ , and electric field intensity on its surface is E. If radius of surface is doubled, keeping σ unchanged, what will be electric field intensity on the new sphere?
  • E/2
  • 2E
  • E/4
  • E
In a certain charge distribution, all points having zero potential can be joined by a circle S. Points inside S have negative potential. A positive charge, which is free to move, is placed inside S.
  • It will remain in equilibrium
  • It can move inside S, but it cannot cross S
  • It must cross S at some time
  • It may move, but will ultimately return to its starting point

Physics-Electrostatics I-70627.png

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    Physics-Electrostatics I-70629.png

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  • Physics-Electrostatics I-70631.png
A sphere of radius 1 m encloses a charge of 5µC. Another charge of –5µC is placed inside the sphere. The net electric flux would be
  • double
  • four times
  • zero
  • none of the above
Three capacitors are connected to a d.c source of 100 V as shown in Fig. If the charge accumulated on the plates of C1, C2 and C3 are qa,qb, qc, qd, qe and qf respectively, then

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    Physics-Electrostatics I-70635.png

  • Physics-Electrostatics I-70636.png

  • Physics-Electrostatics I-70637.png
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